[tex]\dfrac{|AE|}{|AD|}=\dfrac{|AB|}{|AC|}[/tex]
Therefore:
[tex]\dfrac{10}{10+8}=\dfrac{x}{10}\\\\\dfrac{10}{18}=\dfrac{x}{10}\\\\18x=100\\x=\dfrac{100}{18}=5.555\ldots=5.\overline{5}[/tex]
So, none of the choices are correct (5.5 is an approximation).
